Apparatus for regulating a condition



June 4, 1940. 5 x SCHMIDT 2,203,472

APPARATUS FOR REGULATING A CONDITION Filad Feb. 23, 1938 3 She etsf-Sheet 1 June 4, 1940. a. x. scI-IMIDT APPARATUS FDR REGULATING A CONDITION Filed Feb. 23, 1938 3 Sheets-Sheet 2 dunes 68 6 20:30 bEfiE EEE {I w NM 5006 19:30 d2: Esofi 5E S86 52% 5:30 @23 5 25E 5% 58s 5:? 5:30 2: di s5 6: 23 S85 QUE @2555;

EQ QA Aszmoz June 4, 1940. E, x. SCHMIDT 2,203,472

APPARATUS FOR REGULATING A CONDITION Filed Feb. 23, 1938 3 Sheets-Sheet 5 Patented June 4, 1940 UNITED STATES PATENT orrlci:

aware arr-snares roa aacmrmc a coup I'l'ION Edwin x. Schmidt, Whitefish Bay, asalgnor. to Cutler-Hammer, Inc., Milwaukee, Win, a corporation of Delaware Application February 23, 1938, Serial lilo. 192.1188

4 Claim.

invention relates more particularly to a float operated liquid level controlling system.

An object of the invention is to provide a system including a control element operable automatically in a direction, at a rate, and to a degree corresponding to the direction, rate and degree of divergence of a value with respect to another preselected value.

Another object of the invention is to provide a system in which the supply of material or energy is so controlled as to maintain a substantially constant predetermined condition independently of the rate at which material or energy is removed from the system.

Another object is to provide an automatic controlling or regulating device wherein the controlling efifect produced is made proportional to the deviation from a predetermined desired condition, to thereby substantially prevent hunting due to over-regulation.

Another object is to provide control apparatus of the aforementioned character affording an indication of the trend or direction of divergence of the controlled medium from a predetermined or desired condition.

A more specific object is to provide a liquid level controlling device including an inlet valve which is automatically opened or closed to maintain the level of the liquid within certain predetermined limits under conditions of variation in the rate of outflow of or demand for the liquid.

Another object is to provide novel' control means for a valve whereby upon a relatively slow rate of change in the liquid level the valve remains inoperative pending attainment of a predetermined maximum or minimum level of such liquid.

Another object is to provide control means of the character last mentioned whereby upon a relatively rapid rate of change in the liquid level the valve is operated automatically to reduce the rate of change to the relatively slow rate aforementioned; and to eventually reduce said rate of change to zero value upon attainment of a predetermined normal level of the liquid.

Another object is to provide a float operated liquid level controlling system wherein the rate of flow of a liquid into a container is varied substantially instantaneously in response to variations in the rate of outflow of or demand for the liquid.

Another object is to provide a float operated liquid level controlling system which is fully automatic in operation but subiect to manual adiustment to conform to or to compensate for conditions encountered in a given installation.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described; it being understood that the invention is susceptible of embodiment in other forms with- 10 out departing from the spirit and scope of my invention as defined by the appended claims.

In the drawings, Figure 1 is a diagrammatic and schematic illustration of a float operated liquid level con- 15 so Fig. 3 schematically and diagrammatically illustrates a modified form of float operated liquid level controlling system involving use of a single float.

Fig. 4 is a schematic and diagrammatic illusg tration of a control system similar to that shown in Fig. 3, but slightly modified to provide for an increase in the rate of valve operation under conditions of relatively large and/or relatively rapid variations in the rate of net flow of the liquid. w

Referring first to Fig. 1, the numeral 5 designates a container or basin into which liquid. such as water, is supplied through conduit 6, from a suitable source, at a rate dependent upon the degree of opening of a valve i. Liquid is discharged 5 from tank 5 through the medium of conduit 0 at a rate dependent upon a variable rate of demand for the liquid-the particular means for controlling the rateof discharge of liquid from tank 5 forming no part of the present invention. It is to be understood that tank 5 may be of relatively great size, and in practice the rate of demand for the liquid from tank 5 is subject to rapid and relatively wide variations-for instance, an increase or decrease in the rate of demand of as much as two thousand gallons per minute.

It is desirable to maintain the level of liquid in tank 5 substantially constant, or within certain limits relatively to a preselected normal level thereof, notwithstanding the aforementioned variable rate of demand or discharge of liquid from said tank. Accordingly it is primarily desired to operate valve 1 in a direction and to a degree corresponding to the direction and degree of di vergence of the level of liquid in tank from the normal level preselected therefor.

Valve I is operable selectively toward the fully open position or closed position thereof by a split-field reversible motor 9 of well known form, through the medium of a suitable form of speedreducing gearing designated in general by the numeral l0. Energization of motor 9 for operation thereof in a direction to effect opening movement of valve I is subject to closure of the normally open contacts ll of an electromagnetically operable relay l2; and energization of said motor for operation thereof in a direction to effect closing movement of valve I is subject to closure of the normally open contacts l3 of. an electromagnetically operable relay l4. A limit switch I5 is included in circuit in series with the operating winding of relay l2, switch |5 being arranged in any suitable manner for opening thereof, with consequent de-energization of relay l2 and motor 9, upon attainment of fully open position of valve I. In like manner, a limit switch I6 is included in circuit in' series with the operating winding of relay |4, switch l6 being opened in a well known manner for de-energization of relay |4 andmotor 9 upon attainment of closed position of valve I.

Included in circuit in series with the operating winding of relay I2 is an interrupter having normally open contacts H which are adapted to be closed upon engagement therewith of the complementary and relatively adjustable raised portions or cams upon a pair of rotary disks or the like l9, l9, which cams jointly provide the cam surface It! of desired length. Also included in circuit in series with the operating winding of relay I4 is an interrupter having normally open contacts which are adapted to be-closed upon engagement therewith of the complementary and relatively adjustable raised portions or cams upon a pair of rotary disks or the like 22, 22, which cams jointly provide the cam surface 2|. As shown, cam surfaces l8 and 2| occupy a pre-adjusted relatively small portion of the respective peripheries of pairs of disks l9, l9 and 22, 22 and said cam surfaces are preferably arranged at like radial angles to said disks. The pairs of disks I9, I9 and 22, 22 are adapted to be continuously driven by a relatively small motor 23, which is adapted to' be connected across lines U, U through the medium of a manuualy operable main switch 24.

Connected in circuit in series with contacts II is the "low contact 25 of a switch having a contactor 26 which is moved into engagement with contact 25 through the operation of float 21 when the liquid drops a predetermined degree below the normal level 28 thereof illustrated. Thus during engagement of contactor 26 with contact 25 motor 9 will be operated intermittently to effect step-by-step movement of valve I toward the fully open position thereof. The circuit thus provided for motor 9 results from closure of relay |2, the energizing circuit for which may be traced from line L through the left hand pole of switch 24 by conductors 29 and 39 through cam surface 34 which extends throughout at least justed to vary the extent of cam surface 34, up to the complete periphery of said disks jointly.

It follows that for certain installations the switch 3| and the cam operating means therefor may be omitted entirely, the function of switch 3| being hereafter more fully described. The aforementioned circuit may be further traced by conductor 35 through contactor 26 and contact 25, conductors 36 and 31 through contacts |I, during the closed period of the latter, thence through the operating winding of relay l2 and through the contacts of limit switch l5 to conductor 39, and through the right hand pole of switch 24 to lineL. The disk 32, 32 are likewise driven by motor 23, all of the aforementioned pairs of disks being rigidly attached to shaft 33 of motor 23.

Closure of contacts ll of relay l2 completes a circuit for operation of motor 9 to effect movement of valve I toward fully open position, said circuit extending from line L to conductor 39 by conductor 39 through said contacts conductor 40 through one ofthe split field windings of motor 9, and by conductors 4| and 33 to line L. As shown, the disks |9 are so adjusted as to provide a relatively short cam surface l8, equal to, say, one-eighth of the periphery of said disks. As a result of operation of the parts aforedescribed motor 9 will be operated for a period corresponding to, say, one-eighth of the time required for one complete rotation of disks I9, to effect opening movement of valve I, the motor being de-energized and valve I remaining stationary during the remainder of the period of rotation of said disks.

However, the system includes a second float 42 which operates a lever 43 pivoted at 44. Attached to and movable with lever 43 is a pulley or wheel 45 over which passes a belt or strap 46, the respective ends 41 and 49 of which are attached to opposite ends of a lever 49 which is centrally pivoted at 50 to a suitable support, the arrangement being such that belt 46 is under a slight degree of tension so as to provide for frictional driving thereof by pulley 45, but permitting slippage of said pulley relatively to the belt when the latter reaches the limit of its movement in either direction. Rigidly attached to and depending from lever 49 is a lever or rod 5| carrying bridging contact elements 52 and 53 on opposite sides thereof. Rod 5| is movable in one direction to effect engagement of element 52. with a pair of stationary contacts 54 and in the opposite direction to effect engagement of element 53 with a pair of stationary contacts 55. Thus, inasmuch as the liquid in tank 5 is shown at the normal lever 28 thereof, it may be assumed that the liquid was last raised to said level, in which event the float 42 would have been moved upwardly, with consequent engagement of element 53 with contacts 55, as shown.

Under the conditions heretofore assumed, however, the liquid level will have dropped sufliciently to cause engagement of contactor 26 with contact 25; whereas during such lowering of .the liquid level float 42 will have dropped, with consequent engagement of element 52 with contacts 54, at a time prior to engagement of contactor 26 with contact 25, so that the aforementioned contacts I will be shunted by a short-circuit extending from conductor 36, by conductor 56 through contacts 54 as bridged by element 52, and by conductor 51' to and through the operating winding of relay l2, as aforedescribed.

As a result of short-circuiting of contacts l1 aaoaua the duration of the period of operation of motor 8 for effecting opening movement of valve 1 will be greatly increased, such period of operation then corresponding to the relative length of the cam surface 34 which effects closure of the aforementioned contacts 3|. Thus, as shown, disks 32.

,32- are so adjusted as to provide for operation of motor 5 and opening movement of valve I durcated, disks 32, 32 may be so adjusted as to provide a continuous cam surface 34 to provide for continuous closure of contacts 3|, thus providing for a still greater degree of opening of valve 1 during each complete rotation of shaft 33.

If. as a result of opening of valve 1 in the manner aforedescribed, the inflow intotank 5,62% ceeds the outflow therefrom the net flowof liquid into the tank will increase abovenormal or zero and the level of liquid in the tank will, of course, rise. As a consequence of the upward movement of float 42 element 52 will be disengaged from contacts 54, thereby. interrupting the short-circuit around contacts II to decrease the degree of opening of valve 1 during each complete rotation of shaft 33. If the level of liquid in tank 5 continues to rise during such relatively slow rate of opening of valve I per unit of time, the normal level 28 of liquid in tank 5 will be attained, with consequent disengagement of contactor from contact 25. This results in discontinuance of operation of motor 3 pending such a degree of rise of liquid above the normal level 28 thereof as to efiect engagement of contactor 26 (operated by float 21) with a stationary contact 58. In the meantime the rising level of liquid has acted upon float 42 to effect engagement of element 53 with contacts 55, so that the aforementioned engagement of contactor 25 with contact 58 results in intermittent closure of the contacts l3 of relay l4 for a period depending solely uponthe length of cam surface 34, with a relatively large degree of closing movement of valve 1 during each complete rotation of shaft: 33.

The energizing circuit for the winding of relay I4 under the conditions just mentioned may be traced from line L through the left hand pole of switch 24, conductors 29 and 30 through the contacts 3|, during closure of the latter by cam surface 34, conductor 35, through contactor 26 and contact 58, conductors 59 and through contacts 55, as bridged by element 53, conductor 5i through the operating winding of relay l4 (short-circuiting the contacts 20 of the switch controlled by cam surface 21), thence through the contacts of limit switch l5, by conductor 38 through the right hand pole of switch 24 to line L. Valve 1 will therefore be moved toward its fully closed position in a step-by-step manner to degrees determined only by the length of cam surface 34, until the outflow from tank 5 exceeds the inflow thereinto. As soon as the level of liqaid in tank 5 begins to drop, float 42 in moving downward serves to effect disengagement of element 53 from contacts 55, thus interrupting the short-circuit around contacts 28. The latter when thus rendered effective serve to reduce the degree of closing movement of valve 1 during each complete rotation of shaft 38. If the level of liquid in tank -5 continues to drop, then. substantially upon attainment of the normal level '25 thereof, heat 21 will act to effect disengagement of contactor 25 from contact 55 to entirely discontinue operation of motor 5 for closing of valve .1. If the level of the liquid continues to drop, the same will after reaching the normal level 28, effect lowering of float 21, with consequent engagement of contactor 25 with contact 25. In the meantime the downward movement of float 42 will have caused engagement of element 52 with contacts 54, to short circuit contacts ll. Accordingly upon engagement of contactor 25 with contact 25 valve 1 will be intermittently moved toward fully open position through a relatively large degree upon each rotation of shaft 33, as determined by the length of cam surface 34, as aforedescribed.

Referring now to the graphic illustration of Fig. 2, in which the straight line 52 represents the preselected normal level of the liquid within .tank 5 (Fig. 1), and the straight line 53 represents "zero net flow of the liquid; namely, a condition in which the rate of outflow of liquid from tank 5 is exactly equal to the rate of flow of liquid into tank 5. Assuming that the liquid in tank 5 is at the normal level 25 (Fig. 1) as represented at line 52 in Fig. 2, and that the rate of flow of liquid from tank 5 is equal to the rate of flow thereinto as represented at line 53 in Fig. 2. Further assuming that at point 54 in Fig. 2 the rate of demand for the liquid is substantially reduced, with a consequent instantaneous increase in net flow of liquid into .tank 5 as indicated at point it will be understood that float 42 in rising will effect closure of the rising direction switch, as represented by element 53 and contacts 55 in Fig. 1; and float 21 upon a given rise of liquid above the normal level 28 thereof will cause engagement of contactor 25 with the high level contact, 58. Due to shortcircuiting of cam-operated contacts H, as aforedescribed, there will result a relatively large degree of closing movement of valve 1 during each complete rotation of shaft 33, with a consequent decrease in the value of the net flow, as represented by the downwardly angled straight line 55 in Fig. 2, the net flow actually decreasing to a value slightly below zero, as indicated at point 61.

During such rapid closing adjustment of valve 1 there is a decreasing rate of rise of the liquid level, as indicated by the curved line 58, and at point 69 the liquid level begins to fall. As a consequence float 42 in dropping effects disengagement of element 53 from contacts 55 to interrupt the short-circuit around contacts H, which are thereby rendered effective to reduce the degree of closing movement of valve 1 upon each complete rotation of shaft 33. Float 42 in dropping likewise causes engagement of element 52 with contacts 54, but without immediate effect. Inasmuch as at point 61 the net flow into tank 5 is below "zero (that is, the rate of flow into tank 5 is less than the rate of flow therefrom) and valve I is still being closed, although at a relatively slow rate, it follows that the net flow into tank 5 will gradually decrease further, as indicated by the downwardly angled line Ill.

Due to such closing movement of valve I there will be an increasing rate of fall of the liquid level, as represented by the downwardly curved line 1|. At point 12 in Fig. 2, however, the normal liquid level 28 (Fig. 1) will have been attained, with consequent complete interruption of the circuit of motor 9 and discontinuanceof the closing movement of valve 1. As indicated at '18 and 14 in Fig. 2 there will be no change in the net flowjbut inasmuch as the net flow is below fzero" there will be a constant rate of fall of the liquid level from point "to point 15, whereupon, due to closing of the low liquidlevel switch; namely, engagement of contact 25 (Fig. 1) by contactor 28, and prior closure of the falling switch; namely, bridging engagement of element 52 with contacts 54, there will be a rapid opening adjustment of valve 1, as controlled byv contacts 3| (contacts I1 being short-circuited). Therefore between points 15 and 16 the liquid level will begin to rise at an increasing rate, thus increasing the net flow into tank 5 to a point above zero, as indicated at 11. At point 16 due to the rise of liquid level float 42 will act to effect disengagement of element 52 from contacts 54, thereby interrupting the short-circuit around contacts l1, with a consequent slow rate of opening adjustment of valve 1.

The slow rate of opening adjustment of valve I provides an increasing rate of rise of the liquid level between points 16 and 18, with a consequent increase in the net flow, as indicated at 19. At point 18 the normal level 28 of the liquid will be attained, whereupon float 21 will act to effect disengagement of contactor 28 from contact 25. From point 18 to point 88 there will be no adjustment of valve 1, but due to the adjusted position of the valve there will be a constant rate of rise of the liquid level, and the net flow will remain constant between points 19 and 8|. At point 88, float 21 will act to efiect engagement of contactor 28 with high level contact 58; and due to the rising level of liquid float 42 will previously have acted to efiect engagement of element 53 with contacts 55. Therefore, between points 88 and 82 a rapid rate of closing adjustment of valve 1 will be effected, with a consequent rapid rate of variation of the net flow between points 8| and 83.

At point 82 the falling level of liquid will result in disengagement of element 53 from contacts 55, thus interrupting the short-circuit around contacts 28, with a consequent slow rate of closing adjustment of valve 1 until the point 84 is reached, it being understood that due to closing movement of valve 1 there is an increasing rate of fall of the liquid level between points 88 and 84. The net flow will decrease slightly from point 83 to point 85.

At point 84 the normal level 28 of the liquid will be attained, with consequent disengagement of contactor 28 from contact 58 to effect discontinuance of the adjustment of valve 1. Accordingly there will be a constant rate of fall of the liquid level from point 84 to point 88, the net flow remaining constant, as indicated between points 85 and 81. At point 88 float 21 will act to effect engagement of contactor 28 with contact 25, float 42 having previously acted (due to falling of the liquid level) to effect engagement of element 52 with contacts 54. Accordingly there will be a rapid opening adjustment of valve 1 between points 88 and 88, the net flow into tank 5 increasing from a value slightly below zero, as indicated at 81, to a value slightly above zero," as indicated at 89. From point 86 to point 98 there will be an increasing rate of rise of the liquid level,- the rising level acting at point 88 to efiect disengagement of element 52 from contacts 84 to decrease the rate of opening adjustment of valve 1.

There will be a gradual increase in net flow or the liquid between points 99 and 9|; and due to attainment of the normal level 28 of the liquid, as indicated at point 98, float 21 will act to effect disengagement of contactor 28 from contact 25 to again discontinue adjustment of valve 1. In view of the fact that the net flow is slightly above zero value, as indicated by the horizontal line 92, there will be a constant relatively slow rate of rise of the liquid level, as indicated by the slight upward angle of line 92. Under the conditions heretofore assumed the liquid level will continue to rise slowly (line 92) until the predetermined high level or limit is attained, whereupon float 21 will act to effect engagement of contactor 28 with contact 58 (float 42 having previously acted to eifect engagement of element 53 with contacts 55) with consequent temporary rapid closing adjustment of valve 1.

As indicated in Fig. 2, the periods during which no adjustment of valve 1 is required are of progressively increased length or duration, as indicated respectively at 1314; 19-8l; 8581, and line 92. Also as indicated by the liquid level line, starting with line 52, after a relatively wide variation in the rate of demand for the liquid, the system operates automatically in a desirable manner to compensate for such variation and to bring the liquid level to and maintain the same in or adjacent to the desired or normal level thereof, with a minimum of hunting or overregulation. Although in Fig. 2 I have illustrated graphically the functioning or operation of the system in the event of a substantial decrease in the rate of demand for the liquid, it is to be understood that the elements of the system will operate in a similar but reverse manner in the event of a substantial, or in fact, any increase in the rate of demand for the liquid. Such an increase in the rate of demand for the liquid might occur at any point in the operation of the system graphically illustrated in Fig. 2, in which event the parts of the system will operate in a manner which is deemed obvious to compensate for such change in the rate of demand, whereby a predetermined or desired liquid level is attained and thereafter maintained approximately.

Referring again to Fig. 1, it should be noted that I prefer to provide contacts 25 and 58 with lost motion connections between the same and their respective supports 94 and 95, suitable springs 95 and 91 being associated with the respective contacts to bias the same toward the normal positions thereof illustrated. By this means the full movements of contactor 28 in opposite directions may be made to correspond exactly with the corresponding movements of float 21 without imposing an undue burden upon contactor 26 and contacts 25 and 58, such as would occur if said contacts were supported in fixed positions. Suitable means such as nuts 98 and 99 may be provided for adjusting the distances between contacts 25 and 58 and contactor 28 in the intermediate or neutral position of the latter, whereby the high and low limits of the liquid level may be preselected for purposes of each particular installation. For instance, in a given installation it might be desirable to provide for a wider degree of divergence of the liquid level above the normal or preselected level than is provided for divergence thereof below the normal level.

Lever III which is operated by float 21 is pivoted at III andis preferably provided with an adjustable weight I62 to partially counterbalance the float 21 for vertical or intermediate positioning of contactor 26 when the desired liquid level.

exemplified by line 26. is attained in tank5. In

manner the lever 46 which-is operated by float 42 is provided with an adjustable weight I66 to provide for horizontal positioning of lever 46 after closes on the other side.

when the desired level 26 of liquid has been attained. As heretofore pointed out the belt 46 associated with the direction switch moves the elements 52, 56 in one direction or the other, and then permits slippage of pulley 45 with respect thereto. If the direction of movement of theliquid level changes, the direction switch opens immediately on one side thereof and there- Moreover, it should be particularly noted that the net flow 'of the liquid equals zero when theliquid level stops rising and/or falling.

In Fig. 3 I have illustrated a modified form of liquid level controlling system embodying use of a single float designated by the numeral I64.

The tank I65 is provided with an inlet conduit meral I I6.

Operation of motor I66 in a direction to effect movement of valve I6'I toward closed position is subject to control by a relay having normally open contacts III and an operating winding II2. Operation of motor I69 in a direction to effect movement of valve I6'I toward full open position is likewise subjectto control by a relay having normally open contacts H6 and an operating winding I I4. Included in circuit in series with winding I I2 is a limit switch II5 which is associated with valve I61 in any well known manner to provide for opening of said switch upon attainment of fully closed positioning of said valve. Included in circuit in series with winding I I4 is a limit switch I I6 which is likewise associated with valve N1 in any well known manner to provide for opening of said switch upon attainment of fully open positioning of said valve.

Included in circuit in series with one or the other of the operating windings H2 or II4 upon selective pre-setting of the latter for energization is a switch having normally open contacts I I! adapted to be moved intermittently to closed position, as by means of a cam surface II6 upon an element 1 I9, which is adapted to be driven by a continuously operated electric motor I26 connected by conductors I2I and I22 to lines L and L through double-pole switch 24.

The means for selectively controlling energize.- tion of windings H2 and H4 preferably comprises a contactor I26 which is carried by a lever I24 pivoted upon a pin I25 attached to and movable with a cable or rope I26. One end of cable I26 passes over a wheel or pulley I2'I having a fixed pivot I26 and is attached to the float I64 aforementioned. The other end of cable I26 passes over a wheel or pulley I29 having a fixed The lower end I62 of lever I24 is forked at I66 to provide bearings for a wheel or roller I64 which is biased in any suitable manner against a continuous or endless strip or belt of suitable mate-' rial or fabric I65. Strip I65 passes over rolls I66 and I61, the latter being continuously driven at a predetermined rate in, the direction indicated by the arrow by a suitable electric motor I66 through reduction gearing I66, motor I6lbeing connected with any suitable source of energy supply, as, for Instance, lines L, I in an obvious manner.

Contactor I26 when moved toward the right is adapted to-engage a fixed contact I46, and when moved toward the left is adapted to engage a flxed contact I4I. Pin I25 is preferably pro-= vided with a roller I42 which engages a fixed plate or track I46 to maintain contactor I26 in proper alinementjwith contacts I46 and MI in the event of temporary slackening of cable I26 between pulleys I26 and I66. The rate of-movement of strip I65 and the cooperative relationship thereof to the engaging surface of wheel I64 is such that upon movement of pin I25 to the right or left of the position illustrated wheel I64 will tend to retain its initial relationship to strip I65, thus causing tilting or swinging of lever I24 carrylngcontactor I23, with a fulcrum substantially at the point or line of engagement of wheel I64 with strip I65. As will be understood, if the rate of movement of pin I25 in either' direction from the position illustrated is relatively slow (as an incident to a relatively slow rate of rise or fall of the level of the liquid in tank I65) the wheel I64 will, due to its rolling action upon the movingstrip; I65, tend to assume a position in a line parallel with the direction of strip movement, thus reducing the deflecting action upon contact I26 of the movement of pin I25; wherefore engagement of contactor I26 with contact I46 or contact I may not be effected pending a given maximum degree of movement of pin I26 from the intermediate position thereof illustrated. On the other hand, in the event of a rela tively rapid rate of movement of pin I25 (as an incident to a relatively rapid rate of rise or fali of the liquid level), such movement if continued for a relatively short period of time, will result in tilting of contactor l|23 into engagement with contact I46 or contact Mi.

Assuming closure of switch 24 in Fig. 3, let it be further assumed that line '28 represents the preselected normal level of liquid in tank I65. The respective positions of the control parts indicate not only that the normal level 28 of the liquid has been attained, but also that the net flow of liquid is of zero value; that is to say, the rate of flow of liquid into tank I65 through valve I61 corresponds exactly with the rate of demand, or discharge of liquid from said tank through conduit I66. If now there should be a relatively slight decrease in the rate of demand for the liquid the level of the latter would slowly rise above the line 28,.with consequent slow upward movement of float I64 and movement'of cable I26 and pin I25 toward the right. Such movement of pin I25 will cause tilting movement of lever I24, I62, with the point of engagement of wheel I64 with strip I65 as a fulcrum or center, so that contactor I23 will approach contact I46.

Due to the slowness of such movement of pin I25, wheel I64 will likewise move, by reason of the cooperative action of strip I65, toward a position in a line parallel with the, direction of movement of said strip, wherefore the time required for contactor I23 to engage contact I40 will be increased. If the rise in level of the liquid persists, however, contactor I23 will eventually engage contact I40, thereby pre-setting an energizing circuit for winding II2 for completion upon intermittent closure of contacts II1 by the surface II3 of motor driven cam H3. The energizing circuit for winding II2 may be traced from line L through the left hand pole of switch 24, con-' ductor I44 through limit switch H5 and said winding II2, conductor I45, contact I40, contactor I23, conductor I45 through said contacts Ill, when closed, and by conductors I41- and I48 through the right hand pole of switch 24 to line L.

Thus under conditions of relatively slowly rising level of the liquid in tank I05 contactor I23 coacts with contact I40 primarily as a means for limiting the rise in level of liquid within tank I05. On the other hand, in the event of a relatively large decrease in the rate of demand for the liquid, a relatively rapid rate of rise of the liquid level will result. Consequently pin I25 will move toward the right at a rate considerably faster than the rate at which wheel I34 tends to move into vertical alin'ement with said pin, wherefore a relatively large degree of tilting of lever I24, I32 is effected, so that contactor I23 is engaged with contact I40.

Upon closure of contacts III through energization of winding II2, as aforedescribed, a circuit is completed for operation of motor I08 in a direction to effect movement of valve I01 toward closed position, said circuit extending from line L through the left hand pole of switch 24, by conductor I44 through contacts III, conductor I49 through one of the split-field windings of motor I03, and by conductor I48 and the right hand pole of switch 24 to line L. Movement of valve I01 toward closed position is effected in a step-by-step manner for periods depending upon the length of surface II8 (which may be varied by providing a substitute for cam H8, or by providing adjustable pairs of cams like I9, I 3 and 22, 22* shown in Fig. 1) during each complet rotation of cam II8 by'motor I'20.

The aforesaid intermittent movement of valve I01 toward closed position will continue until the level of liquid in tank I05 begins to fall, at which time float I04 in moving downwardly causes movement of cable I26 and pin I25 toward the left to tilt lever I24, I32 in a like direction (with wheel.

I34 as a fulcrum) with consequent disengagement of contactor I23 from contact I40. If, after disengagement of'contactor I23 from contact I40, the rate of discharge through conduit I08 should decrease (due to a decrease in the rate of demand) to an extent such as to result in zero net flow, the level of liquid in tank I05 would remain stationary, so that no adjustment of valve I01 would be required.

On the other hand, if the level of liquid in tank I05 falls relatively slowly pin I25 will continue to move toward the left, during which time wheel I34 tends to move toward vertical position with reference to pin I25, wherefore a relatively long period of time will be required to effect engagement of contactor I23 with contact I. However, if the level of liquid should fall relatively rapidly, pin I25 would move toward the left at a rate considerably more rapid than the rate at which wheel I34 tends to move to vertical alinement with said pin, and the greater degree of tilting of lever I24, I32 toward the left (with wheel I34 as a fulcrum) will reduce the time required for contactor I23 to engage contact I. Engagement of contactor I23 with contact I pre-sets the energizing circuit of relay winding II4 for completion during intermittent closure of contacts II1 by the aforementioned surface H8 01' cam II3. Said circuit may be traced from line L through the left hand pole of switch 24, conductor I44 through the contacts of limit switch IIB, thence through winding II4, conductor I50, contact I and contactor I23, conductor I 46 through the aforementioned contacts II1, when closed, and by conductors I41 and I48 through the right hand pole of switch 24 to line L Closure of the relay contacts II3 completes an alternative energizing circuit for motor I09, said circuit extending from line L through the left hand pole of switch 24, conductors I44 and I5I through said contacts II3, conductor I52 through the other split-field winding of motor I08, and by conductor I48 through the right hand pole of switch 24 to line L. Motor I08 will therefore be operated intermittently to effect step-by-ste'p movement of valve I01 toward fully open position. Such intermittent movement, of valve I01 toward fully open position will continue pending a reversal of the trend of the liquid level; or in other words, pending a rise in such liquid level, which will result in disengagement of contactor I23 from contact I to effect discontinuance of the intermittent operation of motor I03.

It is to be understood that the high level or rapid rise contact I40 and the low level or rapid fall contact I are of the fixed or.

butt typ whereby upon engagement of contactor I23 with either of the same any further movement of cable I25 and pin I25 in the same direction will cause the tail skidor wheel I34 to slip with respect to strip I35.

With further reference to Fig. 3, let it be assumed that, with the liquid at approximately the normal level 28, a relatively rapid rise in the level takes place (due to a relatively large decrease in the rate of demand). As a result lever I24, I32 will be tilted rather quickly toward the right, about the point of contact of wheel I34 upon strip I as a center, to effect engagement of contactor I23 with contact I40, thus providing for intermittent closing movement of valve I01 in the manner aforedescribed. If, as a result of closing movement of valve I01, or as a result of an increase in the rate of demand for the liquid, the rate of rise of the liquid level becomes less than the follower return action (that is, the rate at which wheel I34 in cooperation with strip I35 permits lever I24, I32 to return to vertical position after tilting thereof), such return of lever I24, I32 to vertical position will effect disengagement of contactor I23 from contact I to prevent further adjustment of valve I01 until the liquid has attained substantially the maximum level permitted by the relative position of contact I 40. In the event of a fall in the liquid level, contactor I23 will function in a like manner with reference to contact I".

The liquid level controlling system illustrated in Fig. 4 is in many respects like that illustrated in Fig. 3 and like parts in these figures have been given corresponding numerals of reference. Other parts shown in Fig. 4 which are functionally similar to, but structurally slightly different from, parts shown in Fig. 3 have been given like numerals with the letter a added. Thus in Fig. 4 I prefer to arrange the contacts I40,

a,aos,4vs a 7 MI in less widely spaced relation than are the contacts I40, "I in Fig. 3. With this arrangement contactor I23 will engage contact I45! to eil'ect intermittent closing movement of valve III upon a lesser degree of rise of the liquid from the normal level 24 thereof, and said contactor I22 will engage contact I4I upon a lesser degree of fall of the liquid from said normal level. than is provided in the system of Fig. 3. Also in Fig. 4 contact I40, when engaged by contactor I22,

is yieldable within its supportgl40 against the tion or fully open position, respectively. Up'on such engagement of contactor I23 with contact N I45 (due to a rapid rise in the level of the liduid, or due to a relatively slow rise thereof above the maximum level preselected) if the rise in liquid-level continues notwithstanding the intermittent movements of valve Illl toward closed 25 position, contact I4Il will yield to permit continued movement of portion I24 of the lever toward the right, wherefore the contactor I53 carried by extension I54 will eventually engage the fixed contact I55, thus providing for continuous energization of operating winding II2 by a circuit shunting the cam operated contacts 1. The alternative circuit for winding II2 may be traced from line L through the left hand pole of switch 24, conductor I44 through limit switch U II5, winding II2, conductors I45 and I56, contact I55, contactor I53, conductors I51 and I48 through the right hand pole of switch 24 to line L. I

Similarly, in the event of a rapid fall of the Q liquidlevel, or upon attainment of the minimum level preselected therefor by the normal positioning of contact I4I contact I23 will engage the latter to preset a circuit for relay winding II4 ior intermittent energizatlon thereof, as conll trolled by cam operated contacts iii. If the liquid level continues to fall notwithstanding the intermittent movement of valve I01 toward fully open position, contact I4I, will yield, thus permltting eventual movement of contactor I53 into I engagement with the fixed contact I58, to provide for continuous energization of operating winding II4 by a circuit shunting the cam operated contacts I". This alternative circuit for winding II4 may be traced from line L through II the left hand pole of switch 24, conductor I44 through limit switch II5, winding II4, conductors I50 and I59, contact I58, and thence through contactor I53 to line L as heretofore traced.

The system illustrated in Fig. 4 thus provides Q for either intermittent or continuous adjustment of valve IIl'I toward fully open position or closed position, thereby minimizing the time required to bring the liquid within the maximum and minimum levels preselected therefor; and enabling II the system to more readily and quickly compensate for relatively large variations in the rate of demand for the liquid.

Other uses for systems of the general character hereindisclosed will be at once suggested or 20 obvious to those skilled in the art. While I have disclosed my invention as applied to systems of liquid level control wherein the rate of discharge from the tank is inherently subject to relatively wide variations, as an incident to II relatively widevariations in the rate of demand for the liquid, and wherein the rate of supply of the liquid is varied automatically at a rate and to a degree to compensate for the variations in the rate of discharge; it will be apparent to those skilled in the art that my invention is equally applicable to installations wherein the volumetric rate of supply of liquid is inherently subject to relatively wide variations, and the rate of discharge must be varied automatically at a rate and to a degree to normally render the volumetric 10 rate of discharge substantially equal to the volumetric rate of supply. In such an installation the valve I (Fig. 1) or I01 (Figs. 3 and 4) would be omitted from the supply conduit and alike valve (or an equivalent adjustable flow control- 15 ling device) would be placed in the discharge conduit, the same being so arranged and coordinated with the control mechanism responsive to variations in the level of liquid in the tank as to provide for opening adjustment of the valve to increase the rate of discharge as an incident to a predetermined degree of rise in the liquid level, etc'., or, in other words, to function in substantially the reverse manner from that of the systems hereinabove described.

Also it is to be understood that the adjustable valve herein disclosed is a preferred form of flow controlling means, it being obvious that a motor driven pump or the like may be substituted for the valve, it being only necessary to provide means 50 V operable automatically to vary the speed of operation of the pump driving motor to afford a function corresponding to the aforedescribed opening or closing adjustment of the valve.

As will be apparent to those skilled in the art a the present invention is applicable to control of liquid level, as herein disclosed, or alternatively to control of pressure or temperature conditions;

i and, in fact, to control of any condition of similar character, which condition is affected by a difference in the quantitative flow of material or energy into and/or out of a system.

What I claim as new and desire to secure by Letters Patent is:

1. In a liquid level controlling system, in com- 48 bination, a tank, a source of supply of liquid for said tank, a valve adjustabletoward fully open or closed position to vary the rate of supply of liquid to said tank, means for discharging liquid from said tank in accordance with the rate of demand therefor, a float operable in response to variations in the level of liquid within said tank, a reversible electric motor adapted when energized to effect adjustment of said valve in reverse directions selectively, switch mechanism subject to 55 control by said float and normally operable upon attainment of a predetermined maximum or a predetermined minimum level of liquid within said tank to initiate operation of said motor in one direction or the other to effect closing or 00 opening adjustments, respectively, of said valve, power driven cam means associated with said switch mechanism and normally operable to limit said motor to predetermined periods of operation and inoperation alternately whereby said valve 05 is moved in a step-by-step manner toward closed or fully open position, and a second float operable in response to a change in the direction of variation in the level of liquid within said tank to initially render said cam means ineffective, whereby the degree of adjustment of said valve toward closed or fully open position is substantially increased per unit of time.

2. In a liquid level controlling system, in combination, a tank, a source of supply of liquid for 1 said tank, a valve adjustable toward fully open or closed position to vary the rate of supply of liquid to said tank, means for discharging liquid from said tank in accordance with the rate of demand therefor, a float operable in response to variations in the level of liquid within said tank, a reversible electric motor adapted when energized to effect adjustment of said valve in reverse directions selectively, switch mechanism subject to control by said float and normally operable upon attainment of a predetermined maximum or a predetermined minimum level of liquid within said tank to initiate operation of said motor in one direction or the other to effect closing or opening adjustments, respectively, of said valve, power driven cam means associated with said switch mechanism and normally operable to limit said motor to predetermined periods of operation and inoperation alternately whereby said valve is moved in a step-by-step manner toward closed or fully open position, a second float operable in response to a change in the direction of variation in the level of liquid withfn said tank to initially render said cam means ineffective, whereby the degree of adjustment of said valve toward closed or fully open position is substantially increased per unit of time, and said second float being also operable in response to a reversal of the direction of variation in the level of liquid within said tank to thereupon render'said cam means effective, whereby the rate of adjustment of said valve toward closed or fully open position is substantially decreased.

3. In a liquid level controlling system, in combination, a tank, a source of supply of liquid for said tank, a valve adjustable toward fully open or closed position to vary the rate of supply of liquid to said tank, means for discharging liquid from said tank in accordance with the rate of demand therefor, a float operable in response to variations in the level of liquid within said tank, a reversible electric motor adapted when energized to efiect adjustment of said valve in reverse directions selectively, switch mechanism subject, to control by said float and normally operable upon attainment of a predetermined. maximum or a predetermined minimum level of liquid withinsaid tank to initiate operation of said motor in one direction or the other to effect closing or opening adjustments, respectively, of said valve, power driven cam means associated with said switch mechanism and normally operable to limit said motor to predetermined periods of operation and inoperation alternately whereby said valve is moved'in astep-by-step' manner toward closed or fully open position, a second float operable in response to a change in the direction of variation in the level of liquid within said tank to initially render said cam means ineffective, whereby the degree of adjustment of said valve toward closed or fully open position is substantially increased per unit of time, said second float being also operable in response to a reversal of the direction of variation in the level of liquid within said tank to thereupon render said cam means effective, whereby the rate of adjustment of said valve toward closed or fully open position is substantially decreased, and said switch mechanism being operable by said flrst mentioned float, in response to a predetermined variation in the level of the liquid within said tank, to completely interrupt the energizing circuit of said motor, for the purpose set forth.

4. In a liquid level controlling system, in combination, a tank, means for effecting a flow of liquid into said tank, means for effecting a flow of liquid out of said tank, one of said flows being inherently subject to relatively large variations, means for varying the other of said flows to tend to render said flows substantially equal volumetrically, said last mentioned means comprising a float and switching means controlled thereby in response to a predetermined degree of rise or fall of the level of liquid in said tank, with respect to a normal level preselected therefor, to effect a predetermined variation in the volumetric rate of said other flow, a second float, and switching, means controlled by the latter in response to a reversal of the trend of variation of said liquid level to modify the effect of said flow varying means, to thereby prevent hunting or over-regulation by the latter.

EDWIN X. SCHMIDT. 

